test: exercise once() with varying arguments

cjihrig · MylesBorins · commit a37165a2ccfb · 2017-07-17T14:17:16.000-04:00
This commit regains test coverage for EventEmitter#once() with four or more arguments. To avoid similar regressions in the future, once() is called with enough arguments to cover all of the separate code paths. PR-URL: #13524 Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com> Reviewed-By: James M Snell <jasnell@gmail.com>
diff --git a/test/parallel/test-event-emitter-once.js b/test/parallel/test-event-emitter-once.js
@@ -34,3 +34,23 @@ assert.throws(() => {
 
   ee.once('foo', null);
 }, /^TypeError: "listener" argument must be a function$/);
+
+{
+  // once() has different code paths based on the number of arguments being
+  // emitted. Verify that all of the cases are covered.
+  const maxArgs = 4;
+
+  for (let i = 0; i <= maxArgs; ++i) {
+    const ee = new EventEmitter();
+    const args = ['foo'];
+
+    for (let j = 0; j < i; ++j)
+      args.push(j);
+
+    ee.once('foo', common.mustCall((...params) => {
+      assert.deepStrictEqual(params, args.slice(1));
+    }));
+
+    EventEmitter.prototype.emit.apply(ee, args);
+  }
+}
